1. Field of the Invention
This invention relates in general to magnetic heads and in particular to a multitrack head having an extremely high density of discrete heads (channels) per inch across the face thereof.
The invention also relates to a process for making such multitrack heads.
2. Description Relative to the Prior Art
High density magnetic recording as employed, for example, in connection with the recording of video information is usually done by means of a single-track head which traverses, and coacts at high speeds with, a magnetic tape. Examples of apparatus capable of such recording are quadruplex and helical scan video recorders.
It has long been desired to obviate the need for high relative head-to-tape speed by use of a stationary multitrack magnetic head, whereby each "line" of image signals is simultaneously recorded in parallel on a relatively slow moving tape. Multitrack magnetic heads capable of recording, say, 400 tracks across the one inch width of typical magnetic tape have, to date, been beyond the state of the art. Not only is "track density" a formidable problem, but precise track dimensioning and precise (and uniform) track-to-track spacing are demanding considerations. Indeed, a multitrack head capable of recording 400 tracks per widthwise inch of tape would require that the track-to-track spacing be a mere 0.0025 inches; and given a guard band between tracks, a typical track width would be about 0.0004 to 0.001 inches.
Putting additional stress on the demanding considerations indicated above is the matter of cost. Whereas it might, perhaps, be possible to assemble (tediously) the parts necessary to make a multitrack head of the type under discussion, it is another matter to make multitrack heads, in a high yield process, at low cost. This means that batch fabrication of multitrack heads is a must; and corollarily head design must be such as to be susceptible to batch fabrication.
Consider further that each discrete head of a multitrack head has a coil associated with it; and that each coil has a pair of cooperating leads for connection to a signal processing circuit: This means, for the 400 track head under discussion, 800 leads packed across the one inch width of the head. Needless to say, this is a demanding concern and, attendantly, the head should be of such a design that lead connections to the head can be made easily. Corollarily, the above mentioned batch fabrication process must be one which permits such design.
Representative prior art which may be relevant to the present invention may be found in the following U.S. Pat. Nos.: 3,344,237, issued Sept. 26, 1967 to Gregg; 3,564,522, issued Feb. 16, 1971 to Stevens, Jr.; 3,601,871, issued Aug. 31, 1971 to Pierce; 3,731,005, issued May 1, 1973 to Shearman; 3,986,210, issued Oct. 12, 1976 to Sugaya et al; Re. 29,326, reissued July 26, 1977 to Lazzari et al; 3,893,189, issued July 1, 1975, to Kroon; and 3,983,122, issued Oct. 6, 1976 to Schneider et al.